Telecommunication device

ABSTRACT

A data communication apparatus according to the present invention can be used both in one-wave mode and two-wave mode, and includes: first and second tuning circuits ( 1, 2 ); a power supply circuit ( 3 ) connected to first tuning circuit ( 1 ) for generating power by a signal received by first tuning circuit ( 1 ); an information processing circuit ( 15 ) connected to first tuning circuit ( 1 ) or second tuning circuit ( 2 ) through a switching circuit ( 6 ) and including a detection circuit ( 7 ), a decoder ( 8 ), an encoder ( 10 ) and the like. Information processing circuit ( 15 ) includes a switch control circuit ( 14 ) detecting if the mode of the received radio wave is one-wave mode or two-wave mode in accordance with an output from first tuning circuit ( 1 ) and controlling switching circuit ( 6 ) such that detection circuit ( 7 ) is connected to one of first and second tuning circuits ( 1, 2 ).

TECHNICAL FIELD

The present invention relates to a data communication apparatus whichreceives a radio wave transmitted from an antenna to generate power forcommunication.

BACKGROUND ART

Conventionally, a high frequency tag (RF. TAG), which generates power bya radio wave transmitted from an antenna and transmits information whichhas been stored therein, has been developed and used for a gate of theski lift, gate at the station, sorting of parcels and the like.

The high frequency tag is provided with a non-volatile memory and atransmission/reception mechanism, but not with a power supply sourcesuch as a battery. In addition, power is generated by the received radiowave (a high frequency signal). Thus, the power supply source needs notbe provided therein and information exchange can be performed for a longperiod of time. Further, remote (non-contact) data communication canadvantageously be performed as it is performed by the radio wave.

For a system in which such communication apparatus (hereinafter referredto as “a responder”) is used, one type of radio wave (one-wave mode) ortwo types of radio waves (two-wave mode) may be transmitted from theother communication apparatus (hereinafter referred to as “aninterrogator”). Only one type of carrier with information is transmittedfrom the responder in a one-wave mode, so that the carrier is rectifiedto generate power and also detected to obtain information.

On the other hand, for the responder in a two-wave mode, a first carrierfor generation of power which has not been modulated and a secondcarrier with information are transmitted. Thus, the first and secondcarriers are separately received, so that the first carrier is rectifiedto generate power and the second carrier is detected to obtaininformation.

Since responders used in these modes (e.g., high frequency tags) are ofcourse different in structure, the responder used in one mode cannot beused in the other mode. Therefore, two types of responders are requiredto perform communication in both modes. Accordingly, two types ofintegrated circuits (IC) forming the responders must be manufactured.This disadvantageously results not only in increase in the designing,manufacturing and product cost, but also in complicated management ofthe products (integrated circuit, communication apparatus and the like)for proper use.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide a data communicationapparatus (a responder) which can be used both in one-wave and two-wavemodes.

The object of the present invention is achieved by a data communicationapparatus for data communication with an interrogator including: a powergenerating circuit generating power by a signal having a first frequencytransmitted from the interrogator; and a modulating circuit modulatingthe signal having the first frequency in accordance with responseinformation for an interrogation data when the signal having the firstfrequency transmitted from the interrogator has been modulated inaccordance with the interrogation data, and modulating a signal having asecond frequency in accordance with response information for aninterrogation data obtained by demodulating the signal having the secondfrequency transmitted from the interrogator when the signal having thefirst frequency transmitted form the interrogator has not beenmodulated.

An advantage of the present invention is that one data communicationapparatus (responder) enables communication both in the one-wave modeand two-wave mode, so that two types of data communication apparatusesare not necessary. In addition, since two types of integrated circuitsforming the data communication apparatuses needs not be manufactured,reduction in the designing, manufacturing and product cost is achievedand management of the products (integrated circuits or communicationapparatuses) for proper use is facilitated.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing a structure of a high frequency tagaccording to a first embodiment of the present invention.

FIGS. 2A and 2B are diagrams showing waveforms of signals in the case ofthe two-wave mode.

FIG. 3 is a diagram showing a waveform of a signal in the case of theone-wave mode.

FIGS. 4A and 4B are timing charts shown in conjunction with operationsof an interrogator and responder.

FIG. 5 is a diagram showing a waveform of a signal which is transmittedback to the interrogator from the high frequency tag.

FIG. 6 is a block diagram showing a structure of a high frequency tagaccording to a second embodiment of the present invention.

FIG. 7 is a block diagram showing a structure of a switch controlcircuit detecting the mode related to the received radio wave.

FIGS. 8A and 8B are diagrams showing waveforms of signals input to oroutput from a detection circuit.

BEST MODES FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will now be described in detailwith reference to the drawings. It is noted that the same referencenumerals in the drawings indicate the same or corresponding portions.

FIRST EMBODIMENT

FIG. 1 is a block diagram showing an overall structure of a highfrequency tag (a responder) according to a first embodiment of thepresent invention. As shown in FIG. 1, a high frequency tag 100 receivesand transmits a signal from and to an interrogator 200 having an antenna201 by a radio wave, and is provided with a first tuning circuit 1, asecond tuning circuit 2 and an integrated circuit 110.

Here, first tuning circuit 1 includes a tuning coil L1 tuningapproximately to 13.56 MHz and functioning as a reception antenna, and atuning condenser C1 connected between both ends of tuning coil L1. Asignal having a tuned frequency f₁ which is determined by tuning coil L1and tuning condenser C1 is output from tuning coil L1.

Second tuning circuit 2 includes a tuning coil L2 tuning approximatelyto 3.39 MHz and functioning as a transmission/reception antenna, and atuning condenser C2 connected between both ends of tuning coil L2. Asignal having a tuned frequency f₂ which is determined by tuning coil L2and tuning condenser C2 is output from tuning coil L2.

Further, integrated circuit 110 includes: a power supply circuit 3connected to first tuning circuit 1 and generating power by the receivedhigh frequency signal; an information processing circuit 15; and aswitching circuit 6 which is formed of a semiconductor switch andconnected to a connecting point A in the initial state. Power supplycircuit 3 includes a rectifying circuit 4 rectifying a tuned signal anda regulator 5 connected to rectifying circuit 4 and stabilizing avoltage rectified by and transmitted from rectifying circuit 4. It isnoted that an output voltage of regulator 5 is supplied for each circuitin integrated circuit 110.

In addition, information processing circuit 15 includes: a detectioncircuit 7 connected to switching circuit 6 and detecting (demodulating)a modulated signal (a carrier) shown in FIG. 8A which is supplied fromfirst tuning circuit 1 or second tuning circuit 2 for obtaining aninformation signal shown in FIG. 8B; and a decoder 8 connected todetection circuit 7. It is noted that the information signal shown inFIG. 8B is a digital signal, which is shaped to be a pulse signal havinga waveform in a rectangular shape by a waveform shaping circuit (notshown) and then supplied for decoder 8.

Thereafter, decoder 8 decodes the above mentioned pulse signal inaccordance with a prescribed protocol and outputs a digital data. It isnoted that, generally, decoder 8 also performs serial-parallelconversion.

Information processing circuit 15 includes a memory 12 connected todecoder 8. Memory 12 is accessed by an address designation data outputfrom decoder 8 and, a data stored at the designated address is read.

Information processing circuit 15 includes: an encoder 10 connected tomemory 12; a protocol supplying portion 9 connected to decoder 8 andencoder 10; a pulsating circuit 11 connected to encoder 10; and an Nchannel MOS transistor 13 having its gate connected to pulsating circuit11. Here, an encoding process is performed for the data which is readfrom memory 12 by encoder 10 in accordance with the protocol suppliedfrom protocol supplying portion 9. In most cases, encoder 10 alsoperforms parallel-serial conversion. The data which has been convertedto serial data is in turn converted to a pulse train signal by pulsatingcircuit 11 and supplied for the gate of N channel MOS transistor 13.

Information processing circuit 15 includes a signal transmission line 16connecting switching circuit 6 and detection circuit 7, and the Nchannel MOS transistor has its source connected to a ground node and itsdrain connected to signal transmission line path 16. In the periods inwhich N channel MOS transistor 13 is turned on and off, an impedance offirst tuning circuit 1 or second tuning circuit 2 which is connected tosignal transmission line 16 via switching circuit 6 is different.

Information processing circuit 15 includes a switch control circuit 14connected to detection circuit 7 and detecting a mode of the receivedradio wave for selectively connecting a connecting point A or connectingpoint B by switching circuit 6. Switch control circuit 14 checks anoutput signal from first tuning circuit 1 and, if the output signal isrelated to the one-wave mode, connects connecting point A by switchingcircuit 6, but connects connecting point B by switching circuit 6 if theoutput signal is related to the two-wave mode. It is noted thatconnecting point A is connected by switching circuit 6 in the initialstate and the output signal from first tuning circuit 1 is detected bydetection circuit 7.

Switch control circuit 14 includes a latch circuit 32, a register 33 anda comparator 34 connected to latch circuit 32 and register 33 as shownfor example in FIG. 7. Here, latch circuit 32 latches a prescribednumber of bits of the output signal from detection circuit 7, andregister 33 stores a reference data for the one-wave mode (or two-wavemode). Comparator 34 compares an output signal from latch circuit 32 andan output signal from register 33 and, continues to output “1” if theymatch, but “0” if they mismatch. For example, if register 33 stores thedata related to the one-wave mode, connecting point A is connected byswitching circuit 6 when “1” is output, whereas connecting point B isconnected by switching circuit 6 when “0” is output.

Next, an operation of high frequency tag 100 according to the firstembodiment will be described.

Initially, when interrogator 200 has the two-wave mode, a first signalof a carrier which has not been modulated and which has a frequency f₁shown in FIG. 2A and a second signal which is an arbitrary informationsignal such as “10101” shown in FIG. 2B and a carrier having anamplitude-modulated frequency f₂ are transmitted from antenna 201.

At the time, in high frequency tag 100, first tuning circuit 1 receivesthe first signal and second tuning circuit 2 receives the second signal.The received first signal is converted to power by power supply circuit3, so that the power is supplied for every circuit in high frequency tag100 including detection circuit 7, switch control circuit 14 and thelike as operating power.

On the other hand, the first signal received by first tuning circuit 1is supplied for detection circuit 7 via switching circuit 6 asconnecting point A is connected by switching circuit 6 in the initialstate, and the two-wave mode of interrogator 200 is detected by switchcontrol circuit 14. As a result, connecting point B is connected byswitching circuit 6, and the second signal received by second tuningcircuit 2 is supplied for information processing circuit 15 by signaltransmission line 16. Thereafter, information “10101” from the secondsignal shown in FIG. 2B is decoded by decoder 8, and responseinformation “10110” for the information shown in FIG. 5 is pulsated bypulsating circuit 11. N channel MOS transistor 13 is turned on/off inaccordance with the pulse train signal which has been pulsated bypulsating circuit 11, and the impedance of second tuning circuit 2 ischanged.

For the second signal transmitted from interrogator 200, transmissionperiods T0-T1, T2-T3 and reception period T1-T2 are alternately arrangedas shown in FIG. 4A for interrogator 200. Although a modulated signalsuch as the one shown in FIG. 2B is transmitted in transmission periodsT0-T1, T2-T3, for example, a signal of a carrier at frequency f₂, whichhas not been modulated, is transmitted in reception period T1-T2. Inreception period T1-T2, however, since the impedance of second tuningcircuit 2 which is to be a load of interrogator 200 is changed inaccordance with on/off of N channel MOS transistor 13 by the radio wave,a signal which has been amplitude-modulated in accordance with “10110”shown in FIG. 5 is recognized by detection of the level of the signaltransmitted from interrogator 200. It is noted that this is equivalentto transmission of the response information from high frequency tag 100to interrogator 200 by the radio wave. More specifically, the responseinformation from high frequency tag 100 is transmitted by the radio wavefrom interrogator 200 without transmitting the radio wave from highfrequency tag 100.

FIG. 4B is a timing chart showing the operation of high frequency tag100. As shown in FIG. 4B, the operation of high frequency tag 100 is ina reverse relation with respect to the operation of interrogator 200shown in FIG. 4A.

It is noted that a mode of high frequency tag 100 is switched betweentransmission and reception modes by a command, which is transmitted frominterrogator 200 as a part of information.

When interrogator 200 has the one-wave mode, only a signal of a carrierhaving a frequency f0 which has been amplitude-modulated for example bythe information as shown in FIG. 3 is supplied for high frequency tag100. Here, frequency f₀ is the same as or close to frequency f₁ of asignal including a carrier for the two-wave mode. Thus, the signal shownin FIG. 3 is received by first tuning circuit 1. At the time, no signalis received by second tuning circuit 2, so that an output therefromwould be 0.

The signal received by first tuning circuit 1 is converted to power bypower supply circuit 3. Unlike the case of the two-wave mode, althoughthere is a slight variation in an output voltage level of rectifyingcircuit 4 for rectifying the modulated signal, the voltage is kept at aprescribed level by regulator 5.

The received signal is also detected by detection circuit 7 throughswitching circuit 6, and connecting point A is still connected byswitching circuit 6 as the one-wave mode is detected by switch controlcircuit 14.

It is noted that N channel MOS transistor 13 is turned on/off by thepulse train signal output from pulsating circuit 11, and the impedanceof first tuning circuit 1 is changed. In addition, transmission of theresponse information to interrogator 200 is performed by the radio wavereceived by first tuning circuit 1.

SECOND EMBODIMENT

FIG. 6 is a block diagram showing an overall structure of a highfrequency tag (a responder) according to a second embodiment of thepresent invention. As shown in FIG. 6, the high frequency tag has astructure which is similar to that of the high frequency tag accordingto the first embodiment, except that one end of second tuning circuit 2is not connected to a ground node, signal transmission lines 16 a and 16b are respectively connected through switching circuits 6 a and 6 b toboth ends of second tuning circuit 2, and the high frequency tag isprovided with a comparator 17 having input ends connected to signaltransmission lines 16 a and 16 b, an inverter 18 and a resistance R1which are connected in series between pulsating circuit 11 and signaltransmission line 16 a and a resistance R2 connected between pulsatingcircuit 11 and signal transmission line 16 b, where switch controlcircuit 14 controls switching circuit 6 a and switching circuit 6 b.

More specifically, switch control circuit 14 makes switching circuits 6a and 6 b connect connecting points on the same side. In other words,when connecting point A is connected by switching circuit 6 a, forexample, connecting point A is also connected by switching circuit 6 b.

High frequency tag 101 having such structure also enables datacommunication with interrogator 200 both in the one-wave mode andtwo-wave mode as in the case of high frequency tag 100 according to theabove described first embodiment.

What is claimed is:
 1. A multiple mode capable data communicationapparatus for data communication with an interrogator, said interrogatorbeing adapted to operate in a one-wave mode operation in which a firstsignal of a first frequency modulated with interrogation data istransmitted, or in a two-wave mode operation in which the first signalof the first frequency is not modulated and a second signal of a secondfrequency modulated with the interrogation data is transmitted, saiddata communication apparatus comprising: power generating means forgenerating power from the first signal transmitted from saidinterrogator; demodulating means for demodulating the interrogation dataof the first signal when the interrogator is in the one wave modeoperation, and demodulating the interrogation data of the second signalwhen the interrogator is in the two wave mode operation; switching meansfor switching the demodulating means between a one wave mode operationand a two wave mode operation; and modulating means for modulatingresponse information for the interrogation data obtained by thedemodulated first signal, to a signal of the first frequency when saidinterrogator is in the one-wave mode operation, and for modulating theresponse information for the interrogation data obtained by thedemodulated second signal, to a signal of the second frequency when saidinterrogator is in the two-wave mode operation.
 2. The datacommunication apparatus according to claim 1, wherein said modulatingmeans includes: first tuning means for transmitting and receiving saidsignal having the first frequency; second tuning means for transmittingand receiving said signal having the second frequency, wherein thedemodulating means demodulates a signal received by one of said firsttuning means and said second tuning means and, wherein the switchingmeans connects said demodulating means and one of said first tuningmeans and said second tuning means and connects said demodulating meansand said first tuning means in an initial state; and switch controllingmeans connected to said demodulating means for controlling saidswitching means to connect said demodulating means and said first tuningmeans when said signal having the first frequency demodulated by saiddemodulating means has been modulated and to connect said demodulatingmeans and said second tuning means when said signal has not beenmodulated.
 3. The data communication apparatus according to claim 2,wherein said modulating means (15) further includes differentialamplifying means (17) connected between said switching means (6 a, 6 b)and said demodulating means (7) for differentially inputting the signalreceived by said first tuning means (1) or said second tuning means (2).